The role of acoustic cues in time-­to-­passage judgments : judging time-­to-­passage of looming sounds

Abstract

Estimating the arrival of a moving sound is part of people’s everyday tasks, such as when crossing a street with cars coming from both sides (eg. Winer, 1980 in Rosenblum, Wuestefeld, Saldaña, 1993). Given equal distances, the beginning and ending positions of a moving sound’s source are perceived as closer when moving towards the observer than when moving away (Neuhoff, 2001).This phenomenon called overestimation of looming sounds has been recently studied with a wide range of tasks, from discrete measures of loudness change to Time-­to-­Arrival (TTA). The aim of this study is to explore the ability of subjects to make time-­to-­passage (TTP) judgements in an auditory perception task. White-­noise (binaural sound based on interpolated HRTF in free-­field) was presented moving orthogonal to the frontal plane along a line that passed 1 meter to the right of the participant’s shoulder. Seven constant velocities were combined with s ev en initial dis tanc es , res ulting into 49 lev els of TTP , 24 arriv ing one s ec ond before pas s age and 24 after (see Mouta, Santos, López-­Moliner, 2012). Subjects had to decide whether an approaching sound passed by the ear plane before or after the reference time (1s). In a first experiment we intended to analyse whether the overestimation of looming sounds would occur. Following previous studies on this phenomenon with loudness change (Neuhoff, 2001) and with a TTA task (Rosenblum, Wuestefeld, Saldaña, 1993) we also expected to find overestimation. Results showed that subjects were able to judge TTP (R2= 0.95). Although, regarding overestimation, a clear pattern was not found on individual data. We also raised the question of whether participants could make judgements when the stimuli would not be completely presented, using an occlusion period (at 0.5, 0.7 and 0.9s of stimulus presentation). Participants were instructed to estimate passage, at the moment signalized by a temporal marker (a beep, always presented 1s after the beginning of the stimulus presentation), assuming that velocity and trajectory remained constant. Our expectation was to find a deterioration pattern as the occlusion period increased. Results did not verify this last hypothesis. Accuracy and precision did not vary with different occlusion periods, although adjustment values were lower for the condition with higher occlusion period (R2= 0.73) and higher for the one with lower occlusion period (R2= 0.86). All in all, we did not find the overestimation pattern reported in the literature, even with stimulus occlusion, at least with this kind of task and stimuli.